This invention relates to an arrangement for open-end friction spinning having two rollers serving as friction surface means that are arranged adjacent one another, are drivable in the same rotational direction and form a wedge-shaped gap serving as a yarn formation zone. At least one suction device operates in the area of the wedge-shaped gap, and a feeding device feeds fibers scattered over a limited range of the axial length of the rollers into a scatter zone along the wedge-shaped gap. A withdrawal device withdraws the formed yarn in a longitudinal direction along the wedge-shaped gap. In the scatter zone, along the axial direction of the rollers, sections are provided that have a varying frictional effect, in accordance with the disclosure of German Patent Application No. P 33 21228.7.
According to German Patent Application No. P 33 21228.7 an improvement of the spinning conditions, and thus an improvement of the quality of the spun yarn, can be achieved by the fact that the frictional effect of the rollers is adapted to the forming state of the yarn and is predetermined to suitable values.
The present invention has as one objective, further improving the spinning conditions and thus achieving an improvement of the spun yarn.
This objective is achieved by providing that the sections of the two rollers that are opposite one another have different surface qualities that result in different frictional effects. As a result, especially in the area of the start of the point of the yarn, the yarn formation can be influenced. It also becomes possible to prevent the fibers that are not yet tied up very well from being carried out of the area of the wedge-shaped gap. This contributes significantly to the fact that in the area of the start of the point of the yarn, the fibers cannot leave the wedge-shaped gap with the roller rotating out of the gap.
In a further development of the invention, it is provided that the sections of the rollers assigned to the start of the point of the forming yarn have a surface quality with the relatively lowest frictional effect. This design prevents the start of the yarn point which contains only relatively few fibers from being twisted together too much.
In a further development of the invention, it is provided that the center sections of the rollers have a surface quality within the relatively highest frictional effect. As a result, a high frictional effect exists in that area in which a substantial amount of the final twist is applied to the yarn.
In a further development of the invention, it is provided that the section of the roller rotating out of the wedge-shaped gap that is last in the moving direction of the yarn, has a surface quality that has a higher frictional effect relative to the preceding section of this roller. As a result, in this area in which the already spun yarn is present, a component of force leading out of the wedge-shaped gap is generated so that the yarn can be withdrawn more easily and an excessive false twist is avoided.
In a further development of the invention, it is provided that the surfaces of at least one of the rollers at least in the area of the scatter zone are spark-eroded in order to produce indicated surface qualities. By means of this treatment process of the metallic rollers, a surface structure can be produced that has a precisely determined roughness and thus a precisely determined frictional effect. It will thus be possible to produce the desired surface qualities in the individual sections in a reproducible manner.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.